Dynamic Drift Compensation for Heliostats

Abstract

In central receiver solar power plants the accuracy of heliostat aiming affects directly the plant efficiency. This accuracy depends on multiple factors, some of which are alignment and operation parameters like: canting, pedestal leveling, elevation and zenith orientations, structural deformation, and clock-date timer accuracy to calculate solar position. All of those factors produce drift of the heliostat concentrated radiation spot. The error parameters differ from heliostat to heliostat in a field, and affect each one in a different manner, depending on their location in the field. Trying to compensate by software for every single error parameter, and for each heliostat is a hard, time consuming, and impractical task. Instead of that, a dynamic drift compensator may be used to fix the problem. This corrector works well for certain period of time, requiring a recalibration whenever the heliostat image shifts beyond the tolerance region. This method requires less effort, resulting in a practical solution to drift correction. This work reports on the implementation of a dynamic drift compensator based on a static third order polynomial function, at the Heliostat Test Field in Hermosillo, Sonora, Mexico. The results are compared to theoretical predictions based on error parameters for one heliostat.